Gear-cutter.



T. FAWUUS. GEAR CUTTER. APPLIOATIQN FILED JAN. 9, 1913.

1,096,1 64. Patented May 12, 1914.

UNITED srnrns' PATENT OFFICE.

THOMAS FAWCUS, or PITTSBURGH, PENNSYLVANIA.

GEAR CUTTERh Continuation in 'part of application Serial No. 713,556, filed August 6, 1912.

' 9,1913; Serial No. 740,926.

To all whom it may concern:

Be it known that'I, Tnonas Fawcns, a citizen of the lTnited States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful lnnnovement in Gear-Cutters, of which the tollowip is'a full, clear, andexuvi descri ition, reference being had to the :u-mmpanying drawings, .forming part of this specification. in which Figure 1 is an end view ot a cutter embodying my invention; Fig. 2 is a plan View of the same: Fig. 3 is a detailsectional view showing one of the cutting teeth in elevation: and Fig, l is a plan view of one of the teeth. Fig. 5 is a view similar to Fig. 3, but showing a modified form of cuttingtooth.

The present application is in part'for subject matter disclosed but not claimed in my co-pending application Serial No. 713.556, filed August 3th, 1912.

My invention has relation to gear cutters, and more partieularlv to that class of cuttcrs connnonly known as hobs, which are employed in the manufacture of helical gears and the like, ,and which have the sides and points of their teeth backed off or relieved in such a way as to maintain the reuired shape of cutting tooth to produce. the required shape 'of hub as the teeth are ground back. 4

This invention is particularly applicable to hobs used for generating both spur and helical gears. as in such work by far the greater portion of the metal is removed from the blank by the pointsor peripheral cutting edges. and very little by the sides, the latter in fact nearly forming the proper -ur\'ature ol the sides of the gear teeth, It is. tlurrclorc. obvious that by increasing the umb Y of peripheral cutting edges the speed of the cutter will be proportionately incrcasml. it. however. the number of lvt'tll' in tluacutter is also corrcs 'mndiugly increased thcv will be weakened so that-the speed cannot be maintained without great risk of breaking the cutters.

.\l invention provides for increasing the number of peripheral cutting points whilemaintaining the strength and number of teeth in the cutter. and whereby with u hob of given diameter the number of cutting edges may be doubled. l accomplish this by formingthe hob or cutter withtheusual number of teeth, and thenforming' an extra Specification of Letters Patent.

Patented May 12, 1914;

This application filed January cutting edge on the periphery of each tooth. These secondary cutting edges are only adapted to out. between the outer edges ot the cuts of the main teeth.

Referring to the accompanying drawings, in which I have shown one form of hob embodying my invention, the numeral 2 designates the body of the hole, which is formed with the helically arranged cutting teeth 3, each of which has a cutting edge Z1. These cutting teeth are, in general, of the iisual form. shape and arrangement; but. in ac cordance with my invention ll shape the periphery of each tooth as by a notch 5, or in any other suitable manner to give the tooth an additional peripheral cutting edge 7) which is of the same radius as the cutting edge I). As this additional cutting edge is located at a point well toward the rear of the tooth, it is somewhat; narrower than the main cutting edge. as will he clearly seen by reference to Fig. 4-. This is because of the side relief between points a. and 0 hereinafter described. and which results in narrowing the peripheral edges of the teeth From their point to their rear edges. Each cutting edge backed oil as indicated at T and 8 respectively to provide clearance. Each tooth has two cutting side-edges a, a and two or more peripheral cutting edges I). I). The side edges are relieved gradually from u to and ihe peripheral edges are relieved from I) to the. notch 5 and again From the not h 5 to c. The points 7) and 7" are the. same radial distance from the cen tor of the cutter. It will. of course, be understood that l may form more than one. of the additional cutting edges on each tooth. purtir-. ularl '-on hobs for cutting large pitches. This is illustrated in Fig. 5, in which I have shown n. tooth having three utting edgcs w, r," and a". By the provision of these additional peripheral cutting edges, it. will be seen that the number of cutting edges ma be doubled with a hob of a given diann-ter length. Ilu this nianncr,. thc cutting work of each of the edges -'is' largely reduced. or the speed of the feed-of the cutters can be. increased without increasing the proportion of metal removed by each cutting edge.

The hob may he formed as follows :The blank is lirst turned 'up in the form of a screw; and after it has been turned grooves f) are milled therein in a general longitudinal direction andatapproximately right angles to the helical threads of the hobs. The milling of these grooves forms the cutting faces of the main cutters. The sides of the teeth are then backed ofi in the usual man ner in order to provide proper clearance The peripheries of the teeth arethen inaehined to form the cutting faces for the seeundary teethtij The periphery of the cutter is then backed ofi to form the clearances 7- and 8.

My inventionis not limited to the particular form of cutter as herein shown and described, since it may be applied to other forms.

What I claim. is

1. hob having a plurality of cutting teeth arranged in helical lines, at least. some ot' said teeth having a plurality of peripheral cutting edges, said cutting edges heing of the same radial distance from the center of the hob but of different Widths, and each tooth having a continuous side relief extent-lingfrom the front to the rear edge of the tooth; substantially as described.

2. A ear cutter having a cutting tooth provided with a pl uraiit-y of permheral cutsubstantially as described 4. r-t hob havin a plurality of cutting teeth arranged in helical lines each of said teeth having a plurality of peripheral cutting edges, and a continuous side relief, ertendii'tp; from the front to the rear of the tooth. substantially described.

ln testimon .whereoi, l have hereunto set my hand.

'lHOh'l'tis. FAWCUS. \litnesses H. M. Conwtx,

G120. H. PARMELEE.

relief extending I 

